3.24c

3.24b

3.24a

3.16

3.15

3.14

 chromosomes are the genetic information within a cell they are found in the nucleus. 

DNA

in the structure of a double helix 

in 1 chromosome there are 1000's of genes   ----> each gene carries the information for the construction of a protein-----> the protein gives us the characteristic associated with a gene e.g blood group 

 2: different orgainisms have a different number of chromosomes per cell e.g cat = 38
                                                                                                     chicken = 78
                                                                                              chimpanzee = 42
                                                                                                    humans = 46




chromosomes are known to operate in pairs known as homologous pairs.

homologous nature is based on the length of the chromosomes.

---> gene loci here   <--- will be the same as the                    

                                                                                                                                 gene loci on this side

2 versions of each gene for 1 characteristic. 

 ^

called alleles 

3.1 Sexual and Asexual reproduction

3.1:  Describe the differences between sexual and asexual reproduction

Sexual reproduction	Asexual reproduction
In sexual reproduction there are sexes, male or female.	In asexual reproduction there are no sexes.
Sexual reproduction uses cells called gametes – sperm (male)                               - Egg (female)	In asexual reproduction there are no gametes.
In sexual reproduction cell division called meiosis – ½ the number of chromosomes in a gamete cell . In human adult total number of chromosomes is 46 per cell but in the gamete cell the total number of chromosomes is 23 per cell.	In asexual reproduction there is no meiosis, only mitosis in eukaryote cells. In binary fission in prokaryote bacterial cells the number of chromosomes is maintained constantly. So if there were 20 chromosomes in the process of mitosis it would create to cells each having 20 chromosomes each and being identical.
In sexual reproduction there is fertilisation in which the male and the female gametes fuse together	In asexual reproduction there are:       no gametes à no cell fusion à no fertilisation
In the population of sexual reproduction there is a broad variation – there are differences	In the population of asexual reproduction there is only a small variation which is due to mutation, the majority are identical (clones)

What are eukaryote and prokaryote cells?